Funds for a modern x-ray data collection facility based on electronic area detector instrumentation are requested in this proposal. Rapid changes in DNA technology have led to a growing interest in the structural basis of protein function. Consequently an increasing number of investigators are turning to x-ray crystallography to obtain three-dimensional structures. At Washington University School of Medicine, the growing interest in conformational analysis is hindered by a serious deficiency in instrumentation for x-ray data collection. The only available equipment exists in the laboratories of two crystallographic groups, one in the Department of Biological Chemistry and the other in the Department of Cell Biology and Physiology. This equipment is considerably outdated and scientists in the crystallography groups have already found it necessary to collect diffraction data at resources outside of St. Louis. Continued progress on current and rapidly evolving structural projects within the crystallography groups and throughout the School of Medicine, many relying heavily on recombinant DNA technology, is possible only if this equipment becomes available. By using area detectors to record the x-ray diffraction data, at least a fifty-fold increase in the data collection rate could be obtained. In addition, further advantages would include obtaining of better data, the ability to utilize smaller or radiation sensitive protein crystals, and improved phasing through recordings of anomalous scattering information not readily obtained from large unit cells by diffractometers. The request which follows describes the existing equipment, research projects which would benefit greatly from the instrumentation, and ongoing efforts to train protein chemists in the use of diffraction methods. Most of the projects employ site- directed mutagenesis and/or the cloning of proteins and will be nearly impossible to pursue without the requested instrumentation.